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Looks like a ceramic resonator to me but I am not 100% sure.
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Oct 24, 2021 20:02
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His Divine Shadow posted:Speaking of components, does anyone know what this is? Well 471 on a capacitor would indicate 470 pF. It could be a dual capacitor.
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Oct 24, 2021 21:19
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Could be a resistor network?
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Oct 24, 2021 21:24
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Is there a label next to it on the PCB? Looks like all the other stuff has labels.
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Oct 24, 2021 21:27
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BattleMaster posted:Looks like a ceramic resonator to me but I am not 100% sure. Ceramic resonator is what I thought too. Can you see the reference designator on the PCB?
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Oct 24, 2021 23:03
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Looking at the picture again, it looks like it says CRB next to it.
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Oct 25, 2021 01:19
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Dominoes posted:@Ambrose ive taken a lot of vintage electronics apart but will not state my success rate in restoring them to working order. i like loving around with archaic oddities and scratch-building physically-rooted things like RF components to learn how they work and interact with other systems but my actual EE & Circuit Knowledge is very limited that said, destructively sectioning the component with a fine toothed carbide saw or abrasive cutoff wheel could potentially tell you enough to figure out what it is and source a modern replacement. actually learned a thing or two about capacitor construction that way, but i wonder why i’m no good at fixing things like this 
Ambrose Burnside fucked around with this message at 02:46 on Oct 25, 2021 |
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Oct 25, 2021 02:34
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Cojawfee posted:Looking at the picture again, it looks like it says CRB next to it. Yeah it says CRB1 on it. I found a schematic and here it is. Two capacitors and a resistor? 
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Oct 25, 2021 04:42
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Yay, we're all right
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Oct 25, 2021 05:04
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Capacitor Resistor Boy 1
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Oct 25, 2021 05:08
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So this is a ceramic resonator then? CR makes sense then I guess. I have a hard time seeing what it's doing WRT the battery, perhaps it's entirely incidental and they just led the battery power in there. So what does the 471 mean, 471 kilohertz? It would've made sense if it was 455 since it's a superhetereodyne radio. Though when I bypassed it and applied 6v to the center leg I was able to tue in a channel and if it was broken and a part of tuning I don't think that would've worked. Could it be something like? 54 (ohms) F2037 (capacitance) 471 (khz)
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Oct 25, 2021 06:08
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I am thinking I should power the radio up with mains power and put my oscilloscope probe to each of the side pins of the component and see what it does.... I have been afraid of hooking my oscilloscope to anything with mains power since I don't own an isolation transformer yet, but this is hopefully all low voltage stuff.
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Oct 25, 2021 07:15
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If the power supply inside the radio is not isolated, doing exactly that will ground one side of the component. Which will change the circuit best case, do bad things to your scope worst case
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Oct 25, 2021 07:21
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Yeah best not risk it then. Really need an isolation transformer...
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Oct 25, 2021 07:52
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Just to clarify: The ground clips of your probe are also connected to earth ground, through your scope. The use of the earth ground symbol in that schematic heavily implies that your radio is also using earth ground. There are two ways you could scope it, though: - An isolation transformer, as you are aware. - Just about any multi-channel digital oscilloscope will have a math mode, where you can clip ground to ground, channel 1 to pin 1 of your component, and channel 2 to pin 3 of your component. The scope can then subtract the value of channel 2 from channel 1, giving you a good (and safe) picture of what's going on.
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Oct 25, 2021 08:18
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You almost never need an isolation transformer for any measurement with a scope. It is perfectly fine to have the device & scope earthed to the same voltage, then make single-ended measurements on the circuit. What you should not do is take the connected-to-earth ground clip from a scope probe and clip it to something in the device that isn't ground. (You also should not be floating the scope with either an isolation transformer or a cheater plug). If you want a differential measurement, either use a real differential probe, or use two simultaneous single-ended measurements and subtract
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Oct 25, 2021 08:30
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ante posted:Just to clarify: The radio does not have an earth plug however, and a plastic chassis. So I've been at a bit of a loss to figure out where is ground on this bloody thing. I suppose the negative connection for the battery could be considered ground? When running on battery power I mean. I've got issues understanding the schematic, probably easy for someone who knows this but looking at it, the component CRB-1 is far away from the battery and I don't even see a connection to the battery somehow, yet in real life the negative terminal is right next to the component. I would've thought that would have been reflected in the schematic, unless that's what earth is supposed to be? But it doesn't feel right because the negative lead is between it and some other components. https://i.imgur.com/O9FlSBe.png His Divine Shadow fucked around with this message at 09:08 on Oct 25, 2021 |
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Oct 25, 2021 08:52
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His Divine Shadow posted:The radio does not have an earth plug however, and a plastic chassis. So I've been at a bit of a loss to figure out where is ground on this bloody thing. Everything connected to a ground symbol is wired together. That's a "chassis ground" symbol but in this case the "chassis" is the ground traces on the board. I guess it's used in this case instead of the earth ground symbol because this is battery powered equipment so it's not connected to earth ground when it's being used on battery power. It's a local ground. Most grounds are local grounds and most supplies do some form of isolation because there are lots more ways to start fires and introduce noise when this isn't true. If connecting the negative lead of your supply to a grounded component lead causes the radio to start working, it's probably because the usual ground connection is somehow broken. Do you have a multimeter with a continuity setting? You can disconnect the power and check continuity from the negative side of the power supply connector to any ground on the board and it should show good continuity. If it doesn't, look for broken solder joints or wires. Stack Machine fucked around with this message at 12:39 on Oct 25, 2021 |
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Oct 25, 2021 12:32
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How about this solution, I found another bloody lead on the other PCB board hidden under some cables and plugged it into that and hey presto it works. It makes sense now why the schematics show the battery connection to be where it is, and not near the CRB-1 region. But the existence of the lead that I thought was for negative makes absolutely no sense then, what purpose does it serve, if any? I am also very certain the lead was plugged into there when I first disassembled the radio, but that might have been something I can shove off on the PO, who sold it as broken to me so he might've tried to fix it and failed. Yes.. yes that's it, it's the POs fault...
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Oct 25, 2021 15:04
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Huh. Looking at that schematic, the first thing that jumps out is that this radio has a positive ground (so the supply voltage will read negative if you put the black lead of the meter on ground). That used to be more common when PNPs were more popular but is very strange today. The positive lead of the battery and power supply also don't connect directly to ground, but do it through 2 switched connectors. It's designed to only run off the internal battery when neither an external battery nor the mains connector are inserted. The schematic doesn't make clear what is or isn't on the board but I wonder if the 2 wires you see are the ones out to those switched connectors and back (if they're not mounted on the board).
Stack Machine fucked around with this message at 15:28 on Oct 25, 2021 |
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Oct 25, 2021 15:20
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I've 3d printed a lithophane Christmas tree decoration and would like to add a light to it but have zero experience with electronics. I figure a single LED will be enough of a light source and being a tree decoration I'd like to keep everything as light and compact as possible. I was planning on using a CR2032 coin battery to power it but a cursory google tells me that will power the LED for around 10 hours. Will adding more batteries extend that time or will it just supply additional voltage for those 10 hours? Alternatively, am I going about this completely wrong and should be using something else to power (or even light) it? I'm just muddling through at the moment on what seems logical to me so I'm open to someone telling me "don't use a battery for this, you idiot".
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Oct 25, 2021 16:27
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Tea Bone posted:I've 3d printed a lithophane Christmas tree decoration and would like to add a light to it but have zero experience with electronics. Stacking coin cells increases voltage (which will blow your LED if you don't have something to address that). Hooking them up in parallel will increase current capacity and thus longevity. Is there a reason you can't just put the last light or two from the other lights on the tree behind the lithophane where you're currently planning on putting an LED?
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Oct 25, 2021 16:31
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poeticoddity posted:Stacking coin cells increases voltage (which will blow your LED if you don't have something to address that). Yeah, that's an alternative I've considered. It's a bauble with a lithophane image on it so it doesn't look great with the light behind, but I could print it with a hole sized to poke one of the lights through. It would be nice for the bauble to have its own independent light source, but at the moment I'm trying to gauge how much work that will be. I'm guessing coins aren't ideal for this then? Another possibility would be adding the battery pack externally and hiding it further back in the tree.
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Oct 25, 2021 16:41
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Tea Bone posted:I've 3d printed a lithophane Christmas tree decoration and would like to add a light to it but have zero experience with electronics. Our response to light is pretty non-linear, I'm guessing you looked up the specification for the maximum output of the LED maybe? You could probably get a LOT more life out of it by using a PWM circuit to run it at a lower output and it would probably also give your lithophane better contrast and look more pleasant on the tree. IIRC white (and blue) LEDs are also particularly power hungry, so you may get more life with a red or yellow LED if that would still look nice for your application. You may also be able to add a larger resistor to limit the current and stretch the battery farther, but PWM will be more efficient at the cost of circuit complexity I believe. You can add more batteries in multiple ways. If you add them in series you'll get more voltage but if you add them in parallel you'll get essentially a larger capacity. I'm not sure what circuit you found, but they may rely on the rather high internal resistance of the CR2032 to prevent nuking the LED, so it may not be super straight forward to add more batteries. But I think with a PWM circuit you can probably get enough out of a single cell for the season. I'm not sure what's out there in a ready to go package but there will be tons of circuits using a 555 timer or similar to do this you can find through the googles. Forseti fucked around with this message at 16:44 on Oct 25, 2021 |
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Oct 25, 2021 16:42
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You'll get months with a single LED on a coin cell limited with a resistor to 5mA
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Oct 25, 2021 18:44
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I made a bunch of ornaments last year whose whole trick was using a pair of phototransistors to shine about as bright as whatever was shining on it. I put one in front of the awful flickery LED lights on my tree and they flickered along with them (and ambient room lighting) all thanksgiving-to-new-years, so yeah, you can get about-christmas-tree brightness out of an LED from a CR2032 for months. Now I'm thinking about the fun little circuit I used again. It's like an op-amp voltage buffer with an optical feedback path (the second phototransistor is attached to the LED with opaque heat-shrink).  
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Oct 25, 2021 19:17
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ante posted:You'll get months with a single LED on a coin cell limited with a resistor to 5mA Which is really weird, because coin cells are theoretically rated at like a couple hundred mAh, so you'd expect it to be dead in under a week. But yeah it lasts a lot longer than you might think, as long as you're okay with it being dim. I once put a little project in a glass display case and it had a single orange LED powered by a 2032 or something. It got dim over the course of about two weeks, but for nearly a year afterwards if the lights were off you could still see a faint orange glow.
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Oct 26, 2021 06:50
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Radio turned out nice in the kitchen. Still doesn't wanna play cassettes (low muffled sound) but I am not willing to put effort into that right now. Plays well and the radio tunes in channels well. All I miss is shortwave, only has long and medium wave. Absolutely dead on the LW spectrum. Some russian channels on the MW spectrum. Thinking of getting or building a coil antenna to amplify reception and see what I can tune in.  
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Oct 26, 2021 11:24
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I have a question that's been popping into my mind for the last little while. If you have a battery-operated device (older midi keyboards, stuff made for camping, etc), I presume that if you had an adjustable power supply you could just attach the +/- from the PSU after setting it up to emulate the battery configuration? In any multi-battery case I'd expect you'd have to solder some little plates or wires to the battery terminals such that the current can pass from one to the next like it would in a parallel setup with batteries, and you'd just solder or clip the PSU wires onto the +/- sides. Namely I'd like to make some devices USB rechargable by using Ni-MH battery packs that meet the specifications of the original batteries, or fully powered from the wall by using an ac/dc wall wort with the appropriate specifications (or making a simple circuit to supply the right voltage from as close as I can find for an ac/dc adapter). I have experience with buying the right power adapter for various electronic hobby projects and wiring it into things for arduino projects, adding a capacitor inline from the wall, etc. What am I missing here? Is there some other property of batteries that makes them uniquely suitable for this? Is there some power smoothing or capacitance property in batteries that wouldn't be provided otherwise? e: I know you can get rechargable batteries but this is as much for my own knowledge as it is practicality. VelociBacon fucked around with this message at 17:56 on Oct 26, 2021 |
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Oct 26, 2021 17:54
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No, you don't seem to be missing anything. AAs have really poor electrical properties, so most things that run on them are designed to take really wide voltage ranges with a really high series resistance. So you can do basically anything and the device will usually Just Work. Assume each series battery is 1.5v.
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Oct 26, 2021 18:21
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VelociBacon posted:In any multi-battery case I'd expect you'd have to solder some little plates or wires to the battery terminals such that the current can pass from one to the next like it would in a parallel setup with batteries, and you'd just solder or clip the PSU wires onto the +/- sides. If I'm understanding you correctly: If it's a parallel battery connector, to get more capacity at the voltage of one battery (I haven't seen many devices like this) you shouldn't need to solder the terminals together, they should be one continuous contact already. If it's a series pack, to get more voltage at the same capacity, don't connect the spring terminals together. That would short the power supply and could range from not particularly good to a Bad Thing. The positive lead of the power supply goes to the most positive terminal, and the negative lead to the most negative terminal. That's all.
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Oct 26, 2021 19:25
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One Legged Ninja posted:If it's a parallel battery connector, to get more capacity at the voltage of one battery (I haven't seen many devices like this) ... Total digression, but a lot of wireless mice are like this in my experience. I can run mine with only one battery installed even.
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Oct 26, 2021 19:52
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One Legged Ninja posted:If I'm understanding you correctly: TBH I haven't really looked in at one when I was making that post, thinking about it now yeah you're right, I think they're actually already continuous. I guess I could solder onto wherever is convenient though right? If it's all continuous.
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Oct 26, 2021 20:06
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Personally I would open the thing up and look to see if you can just connect to the wires going to the contacts. Soldering to battery contacts directly is always kinda messy in my experience - if it's a plastic thing, the plastic around the contacts usually melts before you can get it hot enough to accept solder, so then you're just kinda trying not to bump everything and hoping that when the plastic cools back down it'll solidify more or less back in the same shape it was originally. That's assuming it doesn't just burn or melt into a puddle entirely.
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Oct 26, 2021 20:25
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VelociBacon posted:TBH I haven't really looked in at one when I was making that post, thinking about it now yeah you're right, I think they're actually already continuous. I guess I could solder onto wherever is convenient though right? If it's all continuous. You can sort of "unwrap" them into a single stack of batteries in your head (think the stack of D cells in a big flashlight). You want to be connected to each end, one will be positive and one negative. Here's the battery compartment of a radio I have, the blue stuff is all connected together, most positive is marked with the red +, most negative with the black -. They're saying be careful not to hook up to for example the spring and the button all the way left, which could be mistaken for + and - but are actually common to each other (and would dead short your supply).
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Oct 26, 2021 20:32
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VelociBacon posted:TBH I haven't really looked in at one when I was making that post, thinking about it now yeah you're right, I think they're actually already continuous. I guess I could solder onto wherever is convenient though right? If it's all continuous. The normal continuous path would be through the batteries, so no. You need to connect to the endpoints. Edit: I guess you're saying for the parallel case. My mistake. It's a really uncommon configuration, so I misread. If they're parallel, then yes, you can tap in anywhere that's electrically connected to the terminal in question (+ or -)
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Oct 26, 2021 20:37
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One thing that batteries are better at than most mains supplies is noise/ripple. A battery with unchanging load will have a less noisy voltage than a switched mode power supply. Mostly only test equipment uses that though. Devices that do things are probably fine, I wouldn't necessarily expect a conversation on something like a DMM to still meet accuracy specs
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Oct 26, 2021 20:41
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Great, thanks for all the information everyone. I'll post some info if I end up doing this.
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Oct 27, 2021 05:34
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VelociBacon posted:Great, thanks for all the information everyone. I'll post some info if I end up doing this. I've done this dozens of times when I can't be arsed to go to the other room to get the 8 AAAs that my labelmaker needs nor can I be bothered to free up a plug for its power adapter. I just take my bench power supply and hook directly onto the + and - and set the supply to 12V and go. There are a bunch of springs and clips and whatnot on the other end of the battery case that just stare at me, forlorn in their uselessness.
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Oct 27, 2021 08:10
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Apparently you can just buy surprisingly good charge-sensitive preamps for like fifty bucks, and I guess they're used enough that Amazon even has them: https://www.amazon.com/CR-110-R2-1-Charge-Sensitive-preamplifier-Module/dp/B087RV6865 Oh well, building one myself was more fun and educational anyway
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Oct 29, 2021 17:23
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